Intrusion of basalt into frozen sediments and generation of Coherent-Margined Volcaniclastic Dikes (CMVDs)

Graettinger, A. H.; Skilling, I. P.; McGarvie, D. and Höskuldsson, A. (2012). Intrusion of basalt into frozen sediments and generation of Coherent-Margined Volcaniclastic Dikes (CMVDs). Journal of Volcanology and Geothermal Research, 217 pp. 30–38.

DOI: https://doi.org/10.1016/j.jvolgeores.2011.12.008

Abstract

Coherent-Margined Volcaniclastic Dikes (CMVDs) are described for the first time from Askja (Dyngjufjöll), Iceland. These dikes display continuous, coherent glassy margins 5 cm thick and have a variety of clastic interiors comprising vitric tephra, pillow and pillow-fragment bearing lapilli tuffs. CMVDs are interpreted to form when basaltic dikes interact with subglacial ice-cemented volcaniclastic sediments. Formation requires chilling of dike margins, drainage of the dike interior and flooding of the cavity by meltwater, followed by non-explosive mingling of magma, clastics and water. Evidence for ice-cementation includes minimal interaction with the host (< 3 mm peperite), local pillowed dike margins and the preservation of continuous glassy coherent margins along the edge of a drained dike cavity. CMVDs should be present at other volcanic centers with ice-cemented sediments, including the Martian cryosphere.

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